More than 2,000 people in western Africa have been diagnosed with Ebola since March, 2014, according to the World Health Organization, and more than 1,000 of those people have died. The precise number of cases and the mortality rate are speculative; there is no reliable account and many of those who may have been infected have managed to avoid local and medical authorities. The current outbreak, the largest ever for this virus, is far from under control. Two Americans, a physician and a missionary, are recovering in a high-security containment unit in an Atlanta hospital.

Science Life asked infectious disease specialist Emily Landon, MD, hospital epidemiologist, to help us determine the appropriate level of anxiety.

Science Life: This outbreak has already lasted six months and it is still spreading, perhaps faster than ever. Why has this outbreak been so difficult to get under control?

Emily Landon, MD

Landon: This is alarming, but you have to keep in mind certain crucial differences between the United States and parts of Western Africa. Most important is the public health infrastructure we have here. That includes trained infectious disease and epidemiology specialists, the ability to respond quickly, excellent health care facilities with all the necessary protective equipment, good communication tools, including the news media, and the legal authority to quarantine those who have been exposed. None of that has been available in this part of western Africa.

Are US hospitals prepared to handle a case of Ebola, or many cases?

Every hospital in the United States is capable of managing a case and effectively protecting its staff and patients from an Ebola infection. So if a patient comes to one of the hospitals in the US, the teams there will have the tools and skills that they need to protect everybody from getting a case of Ebola. The Atlanta facility where they are caring for the two Americans evacuated from Liberia has a special isolated unit within their research space that’s even safer, but again, any hospital in American should be able to take care of a patient with Ebola safely.

How does Ebola spread?

This is not as contagious as the flu, or as many of the pathogens that we face every day, because it’s not airborne. It requires direct contact, sometimes prolonged contact, with blood and bodily fluids that are infected. They have to get into your mouth, your nose, your eyes, on mucous membranes. It’s not the sort of infectious agent that someone can just cough and you catch it five rows away on an airplane. Most new cases have occurred among people who have been taking care of sick relatives or who have prepared the body for burial.

What if someone leaving western Africa gets on a plane and gets sick?

That is a concern. The incubation period for Ebola is technically two to 21 days, so someone could be exposed and then get on a flight a week later, with no obvious symptoms. Most people get sick eight to ten days after their exposure. The Centers for Disease Control and Prevention has provided guidance to all the airlines about what to do if a patient develops symptoms on a flight and has spent time in one of the affected areas. Flights that are leaving these areas are expected to take care of any sick patient in a way that would best protect the rest of the passengers. That includes having a dedicated crew take care of that person. That crew would not interact with other people on the airplane. They would isolate the ill person in the most remote location possible on the airplane and move any other passengers away, except those already exposed.

What are the typical symptoms?

They often have a prodrome, a set of symptoms that might indicate the start of a disease. This includes fever, muscle aches and body aches. This precedes the classic, disease-spreading Ebola symptoms of nausea, vomiting, diarrhea, clotting disorders and bleeding. Those who have been exposed but do not yet have symptoms can’t transmit Ebola in the usual ways. So patients are not infectious until they become sick.

Many people in Africa do not fully trust western health care and have avoided medical attention. For American or European patients, however, the symptoms are such that they will typically seek out health care. Then we can isolate them appropriately. Once these patients get sick, they get very sick very quickly. They are sick enough to warrant immediate medical care.

How contagious are they?

They are not very contagious if they are not very close by. Unless you are in close contact with a patient you should be safe. Again, this is spread by direct contact with bodily fluids, not through the air. But the virus can survive on surfaces, so any object contaminated with bodily fluids, like a latex glove or a hypodermic needle, may spread the disease.

How lethal is this virus?

The estimates vary widely, usually in the range of 60 to 90 percent mortality. Often, at the beginning of an epidemic, especially of a rare virus, there’s very little understanding of the disease or care for the people who are sick. Ebola is new to western Africa; the previous outbreaks were in Central African nations. The mortality rate for those who get sick early on is high. Once you have a coordinated response, however, after an outbreak has matured, then you start to see more and earlier supportive care. That can reduce the death rate. The mortality in this epidemic is down to about 60 percent now, probably due to the efforts of the humanitarian medical groups responding to the outbreak. But 60 percent is still very high, much more than what any of us wants to see.

That mortality rate is probably higher for immunocompromised patients, who face additional problems, just as they do with other infectious diseases. We know this because many of those in Africa exposed to Ebola also have HIV.

Would that change in the U.S.?

There has never been an outbreak of Ebola in the United States, so it’s hard to know what the death rate her might be. We have much better support systems, better hygiene, better containment tools. That would make a huge difference. That’s why they flew the two American patients back to the U.S.

But keep in mind that this is a lethal disease. People need to take it seriously. American hospitals are capable of taking care of these patients safely and protecting the public, and their own health care providers. They have to be properly equipped and trained to use and decontaminate protective gear correctly. They also have to be consistently, almost obsessively, careful. They have to pay a lot of attention to details. We like to think we are good at that here.